Non-earthquake origin of supraglacial debris on Martin River and Sioux Glaciers, Alaska

Post, Austin

doi:10.3189/s0022143000020311

Cited by 3 publications

(4 citation statements)

References 2 publications

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“…The arcs are higher than the neighbouring depressions, but this may be considered an effect of insulation by the thicker till cover, which protects the underlying ice. This would explain the persistence of the ice-crests under the arcs, and agrees with the observations of Reid (1969[a] and [b], 1970[a] and [b]), Reid and Callender (1965), Post (1967), and Marangunic and Bull (1968), among others. Supraglacial till originated mainly as landslide debris and partially as rock avalanches on the glacier surface.…”

Section: Discussionsupporting

confidence: 90%

“…In only a few places in the world, trees have been observed growing on supraglacial till and, in most of them, the ice has been considered as dead or stagnant (Russell 1893, Tarr and Martin 1914, Odell 1948, Miller 1957, Sharp 1958, Clayton 1964, Post 1967, Porter and Carson 1971, Post and Streveler 1976). In these examples, glacier ice has lost its mobility and it provides a rather stable substratum for pedogenic development and vegetation growth.…”

Section: Introductionmentioning

confidence: 99%

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Moraine In-Transit as Parent Material for Soil Development and the Growth of Valdivian Rain Forest on Moving Ice: Casa Pangue Glacier, Mount Tronador (Lat. 41°10's), Chile

Rabassa

Rubulis²,

Suárez³

1981

Ann. Glaciol.

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Casa Pangue glacier is a regenerated valley glacier, covered by supraglacial moraine of variable thickness (1 to 3 m). Seven moraine in-transit arcs have originated from avalanches falling on the ice from the steep walls at the head of the valley. The debris has been relocated by glacier movement, and vegetation has become established on areas with sediment cover. Primitive soil has developed very rapidly, probably in less than 100 a. Chemical analysis of soil samples show that it is acid (pH 4.6 to 4.7), nitrogen and organic matter are absent, calcium content is low, and potassium content is high. Pedogenic processes are mostly related to intense chemical weathering, under conditions of more than 4 000 mm a−l of total precipitation.The plant communities established on the moraine are essentially similar to the Va1divian rain forest that characterizes the region. The most frequent tree is “coihue” (Nothofagus dombeyi), followed by “teniú“ (Weinmannia trichosperma) and “notro” (Embothrium coccineum). One specimen of N.dombeyi was found to be 18 m tall and 0.62 m in diameter; many others were taller than 12 m and reproduction was abundant. Dendrochronological analysis indicates a minimum age of 45 a for the oldest tree. Other plants found here are shrubs, some hemiparasitic and creeping plants, mosses, lichens, ferns, and fungi.Using air photographs of 1942, 1953, 1970, and our own oblique photographs of 1978, taken from the summit of a neighbouring peak 1 200 m above the glacier tongue, average surface velocity of the glacier tongue was estimated at 22.5 m a−l for the lower and intermediate sectors where the trees are growing. If the total length of the regenerated valley glacier is taken into account, the mean annual movement rate is 35.0 m a−l. If this value is extrapolated over the last 45 a, the trees have moved an average distance of at least 1 000 m in that time.The discovery of established communities (also observed at Río Blanco glacier, southwest of Mt Tronador) on moving ice constitutes an event not previously recorded in glaciological literature. Some significant aspects are discussed: time lapse for soil development on moraine deposits, primary plant succession on moraine deposits, the need of stable ground for plant colonization, the absolute validity of radiocarbon dating of glacier advances using fossil wood found within terminal moraines, and the validity of lichenometric techniques in deglaciated terrain.

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Section: Discussionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

Moraine In-Transit as Parent Material for Soil Development and the Growth of Valdivian Rain Forest on Moving Ice: Casa Pangue Glacier, Mount Tronador (Lat. 41°10's), Chile

Rabassa

Rubulis²,

Suárez³

1981

Ann. Glaciol.

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“…The Great Alaska Earthquake of 1964 brought more outside attention to the Martin River Glacier and it was included in a number of reports on the effects of the earthquake (Grantz et al 1964;Post 1965Post ,1967Ragle et al 1965). Although numerous papers have been written on specific aspects of the glacier by members of the Department of Geology at the University of North Dakota (see for example Clayton 1964;Reid 1969Reid , 1970Reid and Callender 1965;Reid and Clayton 1963;Tuthill 1963Tuthill , 1969and Tuthill and Laird 1966), a more complete report on the geomorphology of this glacier has not been attempted.…”

Section: Previous Glaciological Workmentioning

confidence: 99%

“…There is very little unanimity regarding the definition of stagnant and dead ice, and in most instances the two terms have been used synonymously to refer to ice that is no longer flowing (Flint 1957 (Post 1967), and diminishes to zero at the terminus. The boundary between the active (Bauer's "stationary" ice) and the dead ice is beneath "Miller Lake" (Reid and Callender 1965).…”

Section: Surface Morphologymentioning

confidence: 99%

Geomorphology and Glacial Geology of the Martin River Glacier, Alaska

Reid¹

1970

ARCTIC

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The terminal 17 km. of the Martin River Glacier, and its periphery offer a unique insight into a dynamic system involving land forms, water, plants and animals, all of which are directly dependent upon the glacier regimen. Of the four zones, the Active Ice, Intermediate, Terminal, and Glaciated, the fist is the most extensive. The second two are characterized by forest and brush-covered superglacial drift, less than 1 m. to more than 3 m. in thickness. Ice sinkhole depressions and lakes are common and may drain suddenly via englacial and subglacial channels. Occasional clear lakes are present in the Terminal Zone where ice may lie beneath only 1 to 2 m. of superglacial drift, which is sufficient to protect the lake water from the cold ice and allow successful propagation of aquatic fauna. Trees in the Terminal Zone indicate that this zone was glacially active about A.D. 1650. The outermost terminal moraine and the numerous moraine segments in the Glaciated Zone are probably of Late Wisconsin age. These can be traced to the upper 14 lateral moraines in the valley of the Charlotte Lobe. The soils in the lower 7 moraines are immature to azonal and are probably of Neoglacial age. RÉSUMÉ. Géomorphologie et géologie glaciaire du glacier de la rivière Martin, Alaska.Les derniers 17 km du glacier de la rivière Martin et leur voisinage offrent un aperçu unique sur un système dynamique groupant formes de terrain, eau, plantes et animaux, tous dépendants du régime du glacier. Des quatre zones: zone de glace active, zone intermédiaire, zone terminale et zone glaciée, la première est la plus &endue. Les deux suivantes se caractérisent par de la moraine de surface, d'une épaisseur variant de moins d'un mètre à plus de 3 mètres, couverte de foret et de broussailles. Lacs et dépressions de fonte sont communs et plusieurs se drainent soudainement par des chenaux "englaciaires" et sous-glaciaires. Quelques lacs sont présents dans la zone terminale oil la glace se trouve sous de 1 2 m seulement de moraine de surface, ce qui est suffisant pour protéger les eaux lacustres de la glace et permettre la propagation de la faune aquatique. Les arbres de la zone terminale indiquent que cette zone était glaciairement active vers l'an 1650. La moraine terminale extérieure et les nombreux segments de moraine de la zone englacée sont probablement d'âge fini-wisconsinien. On peut les relier aux 14 moraines latérales supérieures de la vallée du lobe Charlotte. Les sols des 7 moraines inférieures vont de "l'immature" à "l'azonal'' et sont probablement d'âge néo-glaciaire. GEOMORPHOLOGY AND GLACIAL GEOLOGY FIG. 2. Average annual precipitation and temperature for Cordova, Alaska, since 1920.

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Landslides Triggered by the 2002 Denali Fault, Alaska, Earthquake and the Inferred Nature of the Strong Shaking

et al. 2004

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The 2002 M7.9 Denali fault, Alaska, earthquake triggered thousands of landslides, primarily rock falls and rock slides, that ranged in volume from rock falls of a few cubic meters to rock avalanches having volumes as great as 15×106m3. The pattern of landsliding was unusual; the number of slides was less than expected for an earthquake of this magnitude, and the landslides were concentrated in a narrow zone 30-km wide that straddled the fault rupture over its entire 300-km length. The large rock avalanches all clustered along the western third of the rupture zone where acceleration levels and ground-shaking frequencies are thought to have been the highest. Inferences about near-field strong shaking characteristics drawn from the interpretation of the landslide distribution are consistent with results of recent inversion modeling that indicate high-frequency energy generation was greatest in the western part of the fault rupture zone and decreased markedly to the east.

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Non-earthquake origin of supraglacial debris on Martin River and Sioux Glaciers, Alaska

Cited by 3 publications

References 2 publications

Moraine In-Transit as Parent Material for Soil Development and the Growth of Valdivian Rain Forest on Moving Ice: Casa Pangue Glacier, Mount Tronador (Lat. 41°10's), Chile

Moraine In-Transit as Parent Material for Soil Development and the Growth of Valdivian Rain Forest on Moving Ice: Casa Pangue Glacier, Mount Tronador (Lat. 41°10's), Chile

Geomorphology and Glacial Geology of the Martin River Glacier, Alaska

Landslides Triggered by the 2002 Denali Fault, Alaska, Earthquake and the Inferred Nature of the Strong Shaking

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